Arbitrary-precision arithmetic for Swift, in Swift

Swift 5 MIT LiCENSE CI via GitHub Actions


Arbitrary-precision arithmetic for Swift, in Swift


import BigNum
BigRat.sqrt(2, precision:128)  // 240615969168004511545033772477625056927/170141183460469231731687303715884105728
BigFloat.exp(1, precision:128) // 2.718281828459045235360287471352662497759


This module offers two flavors of Arbitrary-precision types that conforms to FloatingPoint.

  • BigRat - Arbitrary-precision rational number.
  • BigFloat - Arbitrary-precision floating point.

In addition to all arithmetic operations that FloatingPoint supports. Most of the functions in <math.h> are offered as static functions. As you see in the synopsis above, all arithmetic functions and operators that are lossy can take precision:Int as an optional argument. When omitted the value of BigRat.precision or BigFloat.precision is used (default:64).

BigFloat.sqrt(2) // 1.41421356237309504876
BigFloat.precision = 128
BigFloat.sqrt(2) // 1.414213562373095048801688724209698078569

BigInt, an arbitrary-precision interger type is internally used and re-exported so you don't have to import BigInt just for that. BigInt is also extended with .over() method so instead of constructing BigRat directly, you can:

BigInt(3260954456333195553).over(BigInt(2305843009213693952)) // == BigRat.sqrt(2)



$ git clone
$ cd swift-bignum # the following assumes your $PWD is here
$ swift build



$ scripts/


$ swift run --repl

and in your repl,

Welcome to Apple Swift version 4.2 (swiftlang-1000.11.37.1 clang-1000.11.45.1). Type :help for assistance.
  1> import BigNum 
  2> BigRat.sqrt(2, precision:128)
$R0: BigNum.BigRat = {
  num = {
    magnitude = {
      kind = array
      storage = 2 values {
        [0] = 6448461645324402335
        [1] = 13043817825332782212
    sign = plus
  den = {
    magnitude = {
      kind = array
      storage = 2 values {
        [0] = 0
        [1] = 9223372036854775808
    sign = plus

From your Xcode Projects.

Simply add the package from Package Dependencies tab of the Project. Enter in the search field and click [Add Package]

Now you are able to import BigNum.

Now all you have to do is build and enjoy!

If you enconter errors like Missing required module '_NumericShims', try cleaning up your ~/Library/Developer/Xcode/DerivedData.

From Your SwiftPM-Managed Projects

Add the following to the dependencies section:

  url: "", .branch("main")

and the following to the .target argument:

  name: "YourSwiftyPackage",
  dependencies: ["BigNum"])

Now all you have to do is:

import BigNum

in your code. Enjoy!


Swift 5 or better, OS X or Linux to build.


  • Swift Tools 5.0.0
View More Packages from this Author


Last updated: Mon Mar 13 2023 08:08:02 GMT-0500 (GMT-05:00)